Translatable fiber stripper

ABSTRACT

A system for stripping an optical fiber includes a source of air and means for generating very short bursts of air. A heater heats the bursts of air to a temperature sufficient to remove the outer coating from an optical fiber, while maintaining the air isolated from the heat source. A single burst of heated air removes the outer coating of an optical fiber, within less than about one second. A series of closely spaced bursts or a prolonged burst of heated air may be used to remove an expanded length of fiber coating. Stripping may include translation of the fiber or the heater or portions thereof. The stripper may be configured to strip several loaded fibers or a single fiber.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continiuation-in-part of U.S. Application Ser. No.09/977,107 filed on Oct. 12, 2001 (now U.S. Pat. No. 6,402,856 B1),which is a continuation in part of Ser. No. 09/724,001, filed on Nov.28, 2000 (now abandoned), which claimed the benefit of priority fromU.S. Provisional Application Ser. No. 60/306,843, filed on Jul. 20,2001, U.S. Provisional Application Ser. No. 60/307,297, filed on Jul.23, 2001, and U.S. Provisional Application Ser. No. 60/310,172, filed onAug. 3, 2001.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

REFERENCE TO MICROFICHE APPENDIX

Not applicable.

FIELD OF THE INVENTION

This invention relates generally to stripping optical fibers, and inparticular to a method and apparatus for rapidly and efficientlystripping optical fibers without using chemicals and without reducingthe tensile strength of the fiber.

BACKGROUND

Fiber optic cables are widely used in modern optical devices and opticalcommunications systems. Optical fibers are usually coated with aprotective layer, for example a polymer coating, in order to protect thesurface of the fiber from chemical or mechanical damage. It is necessaryto remove the protective coating in order to prepare the fibers to becleaved and spliced, or in order to further process the fibers tomanufacture optical devices such as optical sensors and other opticalcommunications network components.

Conventional stripping methods include mechanical stripping, chemicalstripping, and thermal stripping. These methods all suffer from a numberof defects. Mechanical stripping typically involves a stripping tool,similar to a wire stripper, which cuts through the coating and scrapesit off. A major disadvantage is that mechanical stripping typicallynicks or scratches the glass fiber surface, eventually leading to cracksand to a degradation in the tensile strength of the fiber. By way ofexample, the tensile strength of an optical fiber may be reduced fromabout 15-16 pounds before mechanical stripping to about 3-5 pounds aftermechanical stripping. The optical fiber's longevity is thereby reduced.

Chemical stripping uses solvents or concentrated acids to remove thepolymer coating. In the prior art, acid stripping is often performedusing a sulfuric nitric mixture that includes about 95% sulfuric acidand about 5% nitric acid. While this prior art method reduces tensilestrength degradation, an acid residue may typically be left on the fibersurface at the splice point. Therefore, using chemical stripping ontitanium dioxide color coded fiber degrades the splice strength. Also,chemical stripping as performed in the prior art is very costly.Finally, there are major safety concerns inherent in chemical strippingmethods. Ventilation and safety equipment may be needed when using acidsfor the stripping process. Human operators performing acid strippingrequire facilities having well-ventilated areas, preferably with exhaustor ventilation hoods for removing acid fumes. They may also requireprotective gear, such as protective clothing and gloves for avoidingacid burns, and protective breathing apparatus for protection from acidfumes in the air. Storing, handling, and transporting the acids are alsoextremely hazardous.

Thermal stripping processes use heat to remove the coating. Inparticular, hot air stripping methods have been used in the prior art,in which heat (e.g., at about 470° C.) is applied to the polymercoating, causing the polymer coating to heat to a break temperature, atwhich point the removal of the coating begins. Some prior art hot airstripping methods, such as disclosed for example in U.S. Pat. No.5,968,283, involve translation of the fiber optical cable. The fiberoptical cable is moved over the heat source so that heat directly fromthe heat source is applied along the optical fiber cable betweenselected points, causing the corresponding polymer coating to curl anddrop off the optical fiber.

These hot air stripping methods suffer from a number of disadvantages.For example, polymer coating curls can remain attached to the fiberoptical cable. To prevent the polymer coatings from remaining attachedto the optical fiber, it may be necessary to split the polymer coatingfrom the optical fiber at two points, before attempting to curl asection of the polymer coating off the optical fiber. Finally, theseprior art methods tend to expose the heated air stream to carbon oroxidizing metals from the heat source, so that particles of carbon oroxidizing metals are deposited on the fiber during the heating process.When such unwanted particles are deposited on the fiber, the tensilestrength and performance characteristics of the fiber may becompromised.

Another disadvantage of methods such as the method disclosed in U.S.Pat. No. 5,968,283 is that these methods use a hot air heat source thatmust generate heat at the break temperature, before starting to heat thepolymer coating. This usually requires a flow of hot air for a period oftime, before each stripping process begins. Thus, there tends to be arelatively long ramp up time. Devices such as heat shrink guns rated at1500 Watts, which generate forced air at a temperature of about 470degrees Celsius, are thus used as the heat source in these prior artmethods. When splicing cycles are repeated, the flow of very hot air maybe continuous. A continuous flow of very hot air can make it extremelyhot and dangerous for the operator and cause a great deal of wastedenergy.

It is an object of this invention to provide a method and apparatus forstripping fiber optical cable that do not suffer from the disadvantagesdescribed above. In particular, it is an object of this invention toprovide a method and apparatus for stripping fiber optical cable withoutusing chemicals, and without reducing the tensile strength of the fiber.It is another object of this invention to provide a method and apparatusfor stripping fiber without curling the polymer coating. It is anotherobject of this invention to provide a method and apparatus for strippingfiber more rapidly and efficiently, as compared to prior art methods,and without leaving any coating residues on the fiber. It is yet anotherobject of this invention to provide a method and apparatus for strippingfiber that can be used to strip titanium dioxide color coded fiber,without degrading the splice strength of the fiber. It is yet anotherobject of the present invention to provide and method and apparatus forstripping optical fiber that does not require a continuous flow of hotair. It is another object of the present invention to provide a methodand apparatus for translating the stripper or portions thereof, thefiber or some combination thereof

SUMMARY OF THE INVENTION

The present invention provides a system and method for heat stripping anoptical fiber (e.g., titanium dioxide color coded fiber). A short,heated burst of air is injected from a forced air heat source, andapplied to one or more portions of the optical fiber. A short burst ofair lasts less than about one second, and has a temperature of about700-1100 degrees C. This is useful in quickly stripping a portion of thefiber cable (or spot stripping). The stripper may be a translatablestripper, whereby the stripper or portions thereof, the fiber(s), orsome combination thereof, are translatable. In such a case, prolonged ormulti-burst techniques may be used to strip one or more extended lengthsof one or more fiber optic cables. In either case, due to the hightemperature, the outer coating of the optical fiber is immediatelyremoved, without degrading the original tensile strength of the fiber.No coating residue remains on the fiber, and no curling of the coatingoccurs. While heated air is used in a preferred embodiment of theinvention, other embodiments may use other substances, such as othergases and fluids.

A system for stripping an optical fiber in accordance with the presentinvention includes an air source and means for generating short burstsor streams of air from the air source, by releasing compressed airduring short periods of time. Typically, each short burst of air lastsless than one second. However, for stripping extended lengths of fiberthe burst of air may have a longer duration, e.g., 4-5 seconds.

In one embodiment of the invention, the means for generating bursts ofair includes an air pressure generator for creating air pressure, an airpressure controller for controlling air pressure, and an air flowregulator for regulating the flow of air out of the means for generatingbursts of air, so as to controllably release compressed air from themeans for generating bursts of air during very short time intervals. Inone form of the invention, the air flow regulator may be a solenoidvalve controlled by a timer.

The optical fiber stripping system further includes a heater for heatingthe bursts of air to a temperature sufficient to remove the outercoating from the optical fiber with a single burst. Typically, therequisite temperature is from about 700 degrees Celsius to about 1100degrees Celsius. The heater heats the air bursts without bringing theair into contact with the heat source of the heater. In this way, theair avoids exposure to unwanted contaminating particles from the heatsource, such as carbon or oxidized particles. The unwanted particles arethus prevented from being deposited on the fiber, and from reducing thetensile strength or performance characteristics of the fiber. The heatercan be used to efficiently heat substances other than air, such as othergases and fluids.

The heater includes a heater core having a heat generating element. Theheater core supplies heat to a heat chamber. An air conduit receives airfrom the means for generating bursts of air and is preferably configuredto also receive heat from the heater core, thereby preheating the air.Along with a heat chamber outlet port, the air conduit and heat chamberform an isolated air transport path. When air is injected from the meansfor generating bursts of air into the air conduit, heat generated by theheat generating element in the heater core is transferred to the airwhile the burst of air flows through the conduit and through the heatchamber. In this way, the air stream is heated to a temperaturesufficient to strip an optical fiber, while remaining isolated from theheat generating element in the heater core. An air output nozzleconnected to the outlet port of the heat chamber directs the heatedburst of air at the portion of the optical fiber to be stripped. Theouter coating of the fiber is vaporized and removed almost instantly. Inother forms, preheating in an air conduit may not be provided.

In various embodiments, the stripper or portions thereof aretranslatable with respect to the fiber. In other embodiments, the fibermay be translatable with respect to the stripper, or portions thereof.In such translatable strippers, multiple bursts of air may be used tostrip an extended length of fiber, different areas on the same fiber,multiple fibers using the same output nozzle, or some combinationthereof. Otherwise, several output nozzles may be provided, eachconfigured for alignment with different fibers or different areas of thesame fiber, and the heat chamber outlet port may be translatable (orinclude a translatable extension member) such that the outlet portcouples to each of several output nozzles. Otherwise, multiple outletports and output nozzles may be provided, and one or more of those maybe translatable.

The present invention features a method for stripping one or moreoptical fibers. The method includes delivering bursts, i.e., each burstof air characterized by a relatively short duration in time. The airbursts are injected into a heater via an isolated air transport path.The heater includes a heat chamber and a heat generating element. Thebursts of air are heated within the heat chamber to a temperaturesufficient to vaporize the outer coating from the fiber, without the airbeing exposed to the heat generating element. In one form, a singleshort burst of air of about 1 second or less is directed at a portion ofthe optical fiber to be stripped, so as to thermally remove the outercoating from the optical fiber within less than one second, i.e., spotstripping. In another form, continuous stripping is used to strip anextended portion of a fiber. Continuous stripping may be accomplishedusing a multi-burst technique where a series of closely spaced shortbursts are applied to the extended portion of the fiber. In anotherform, continuous stripping is accomplished by a prolonged bursttechnique where a burst of about 4-5 seconds, as an example only, isapplied along a length of fiber to be stripped. The actual duration ofthe prolonged burst is determined as a function of the length of theportion of the fiber to be stripped. Spot stripping or continuousstripping may be used with a single portion of a single fiber, differentportions of the same fiber, or on different fibers. In variousembodiments of the method, the output nozzle or stripper istranslatable, the fiber or fibers are translatable, or some combinationthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict preferred embodiments by way of example, notby way of limitations. In the figures, like reference numerals refer tothe same or similar elements.

FIG. 1 provides a schematic block diagram of a system for stripping anoptical fiber, constructed in accordance with the present invention.

FIG. 2A provides an overall plan view of a heater and FIG. 2B provides atop view of an arrangement of heater exchange elements and air path, inaccordance with the present invention.

FIG. 3A provides a side view of the inner heat chamber.

FIG. 3B provides a top view of the inner heat chamber.

FIG. 4A provides a side view of the spiral-shaped air conduit thatsurrounds the heater core.

FIG. 4B provides a top view of the spiral-shaped conduit.

FIG. 5A provides a top view of a heater core, constructed in accordancewith a preferred embodiment of the present invention.

FIG. 5B provides a side view of a heater core, constructed in accordancewith a preferred embodiment of the present invention.

FIG. 6 provides a cross-sectional view of a heater core, constructed inaccordance with another embodiment of the present invention.

FIGS. 7A-7H show various embodiments of translatable strippers, inaccordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a system and method for ultra-faststripping of the outer coating from an optical fiber, without usingchemicals and without reducing the original tensile strength of thefiber. The heating efficiency is significantly improved, as compared tothe prior art.

FIG. 1 provides a schematic block diagram of a system 10 for stripping afiber optic cable 50, constructed in accordance with one embodiment ofthe present invention. In overview, the system 10 includes a source ofair 12, and means 14 for generating bursts of air, or air streams, fromthe air source. While air is used in the embodiment illustrated in FIG.1, other substances can be used, including but not limited to gases andfluids. The system further includes a heater 16 for rapidly heating thebursts of air from the air source to a temperature sufficient to removethe outer coating from the fiber optic cable 50. The heater 16 can beused to heat substances other than air, such as other gases and fluids.

Preferably, the air source 12 supplies air through an air filter 34 tothe means 14 for generating bursts of air. In this way, the means 14 forgenerating bursts of air receives air that is free of contaminants, suchas oil or oxidized particles. A desiccant may also be added to the air,but the need or desire for use of the desiccant will often depend on thequality or purity of the air provided by air source 12.

In the embodiment of FIG. 1, the means 14 for generating bursts of airincludes a pressure pump 22, a pressure vessel 20, a pressure switch 21,an air pressure controller 24, and an airflow regulator 26. Pressurepump 22 delivers filtered air to pressure vessel 20, thereby creating apressure buildup in pressure vessel 20. The air pressure controller 24controls the air pressure created by the pressure pump 22 within thevessel 20, and also controls the release of pressurized air pressurefrom pressure vessel 20. A pressure switch 21 can be used with the airpressure pump 22, in order to limit and maintain the pressure in thepressure vessel 20 under control of pressure controller 24.

The airflow regulator 26 is responsive to the air pressure controller24, and regulates the flow of compressed air out of the pressure vessel20, so as to release compressed air at desired times to create bursts ofair. The airflow regulator 26 may include a solenoid valve 28, which canbe used to release the air pressure from the pressure vessel 20 for veryshort time intervals, creating the burst effect. An adjustable timer 30(e.g., a timer circuit), preferably including an embeddedmicroprocessor, can be used to control the on/off switching of thesolenoid valve, and thereby control the duration of the burst. A “Go”device or button 40 may be included to initiate the release of a burstof air, and may be in operative communication with the timer 30 or, inother embodiments, directly with the solenoid valve 28.

In manual operation, the “Go” device 40 can be a mechanical, electrical,or electromechanical button, switch or device. In an automated context,the “Go” device can be a controller, interface or port configured toreceive a control signal. The burst of air released from the pressurevessel 20 is injected into an input port 118 of heater 16. A powersupply 42 can be provided to supply power for the heater 16 and thetimer 30, and an on/off switch 44 may regulate one or more of the heater16, the pressure controller 24, and the pressure regulator 26 or theentire stripper system. A temperature controller 210 may be included tohelp regulate the heater 16 output, based on a temperature valuefeedback, as discussed in greater detail with respect to FIG. 3A below.The temperature controller 210 may also take power from power supply 42,as is shown in FIG. 1.

FIG. 2A provides an overall plan view of a heater 100, representative ofheater 16 of FIG. 1, constructed in accordance with one embodiment ofthe present invention. In a preferred embodiment, the heater 100 is aprocess air heater that can achieve the extremely high air temperaturesrequired to strip optical fiber, typically between about 700 degreesCelsius to about 1100 degrees Celsius. The heater 100 provides a uniquecombination of low cost, high efficiency, small size, purity, andmaximum temperature. The heater 100 is designed so as to enclose most ofthe heat within an inner heat chamber 114, until heated air is releasedfrom an output nozzle 205 coupled to or integral with an outlet port 201of the heat chamber 114. Preferably, the heater 100 has less than 10minutes of ramp time, from room temperature to the desired temperature.The heater 100 is capable of achieving and maintaining air temperaturesin excess of 1050 degrees Celsius, for long periods of time. The powerrequirement for the heater 100 is preferably a maximum of about 500watts, at 120 volts AC. In the illustrated embodiment, the heater 100 isabout 10 inches long and about 4 inches in diameter.

According to the present invention, effective stripping of an opticalfiber requires that the process air heater 100 not introducecontamination of any kind to the air. If introduced into the air, thecontaminating particles could deposit themselves onto the optical fiber,when the heated bursts of air from output nozzle 205 are applied to thestripping length of the optical fiber. This would eventually lead todegradation of the splice strength and performance of the fiber.Accordingly, the filtered air received by the means 14 for generatingbursts of air remains isolated within an isolated air transport pathuntil it is output by the stripper.

An isolated air transport path in accordance with the present inventionis comprised of heat chamber 114, a means to couple to said means 14 ofgenerating bursts of air to an input port 141 of said heat chamber 114,and the heat chamber outlet port 201. In the preferred form, an airconduit 116 couples, at an output end 117, to the heat chamber inputport 141 (see FIG. 3A). The air conduit 116 includes the input port 118,into which air from the means 14 of generating bursts of air areinjected, for example using an air injection nozzle at said input port118. Upon injection of air into the air conduit 116, heat from theheater core 112 (see FIGS. 2B and 6) is transferred to the injected airwhile the air flows through the air conduit 116 and into the heatchamber 114. In this way, the air is pre-heated to aid in achieving thehigh temperatures necessary for stripping fiber optic cable, whileavoiding any direct exposure to the heater core 112.

An air output nozzle 205, coupled to or integral with the outlet port201, is used to direct heated bursts of air from the heat chamber 114 tothe optical fiber to be stripped. In some embodiments, the air outputnozzle 205 may be easily removable, facilitating the interchanging ofnozzles, wherein different nozzles are provided having different outputdimensions and characteristics, depending on the characteristics anddimensions of the object to be stripped.

In contrast to prior art methods, in which a continuous flow of exposedhot air is generated in order to strip an optical fiber, in the presentinvention the heat is enclosed in the chamber 114, until one or morewell defined bursts of hot air is generated at approximately 700 to 1100degrees C. The heated burst of air is directed at a portion of the fibercoating to be stripped. As previously mentioned, a short burst lastsless than about 1 second and a prolonged burst has a duration chosenbased on the length of the portion of the fiber to be stripped, e.g., upto about 5 seconds. The entire polymer coating to be stripped is removedalmost instantly, without curling. Also, there is very little or no rampup time or flow of hot air between cycles or uses.

In the present invention, the heater 100 includes a heat exchanger. Theheat exchanger enables the heater to heat the air to the desired hightemperatures, while preventing exposure of the air to any unwantedparticles from the heat generating element of the heater, such asoxidized metal particles or carbon. The heat exchanger is designed tomaximize convection, conduction, and radiation. The use of a heatexchanger and isolated air path, together with the air filter 34described in conjunction with FIG. 1, prevent oxidized or otherwisecontaminated heater particles from coming into contact with the fiber.This is one of the reasons why the method and system of the presentinvention yield substantially higher and more consistent tensilestrength of the stripped fiber, as compared to prior art methods.

In a preferred embodiment, the heat exchanger includes a heater core 112(further illustrated in FIGS. 5A-B and FIG. 6) configured to generateheat and disposed to transfer heat to the heat chamber 114 and,preferably, air conduit 116. In one embodiment, the heater core 112 maybe a replaceable component of the heater 100. By using a replaceableheater core, the cost and frequency of replacing a burned out heater canbe minimized, and the heater can have a life-span of at least 5000+hours. The heater core 112 preferably has a cylindrical shell structureand includes a heat generating element 113 (see FIG. 6). In a preferredembodiment, the heat generating element 113 is a conductive filament,such as a heater wire, that generates heat when an electrical potentialis applied across the filament.

FIG. 2B provides a top view of the arrangement of the heat exchangerelements and the isolated air path, in accordance with the preferredembodiment. The air conduit 116 encircles the outer surface of theheater core 112 and the heater core 112 substantially encircles theheater chamber 114, having outlet port 201. Accordingly, a gap or voidregion 119 is formed between the inner heat chamber 114 and the outerspiral air conduit 116, to accommodate placement of the heater core 112therebetween. Therefore, the gap region 119 is also substantiallycylindrical, and is sized so as to allow the heater core 112 to beeasily press-fit into the gap region 119. In a configuration in which areplaceable heater core 112 is used, the gap region 119 allows thereplaceable heater core 112 (and heat generating element 113) to beeasily inserted therein and removed therefrom.

The heat chamber 114 serves to enclose within the chamber most of theheat generated by the heat generating element 113 of the heater core112, until a heated air burst is released from the chamber. When airconduit 116 is used, the air received by heat chamber 114 is preheated,so less heating within the heat chamber is needed, thus the heatingprocess is relatively quick. If the air is not preheated, substantiallyall heating is accomplished in heat chamber 114. In either manner, theair within heat chamber 114 is fully heated to desired temperature forstripping and remains isolated from the heater core 112 and its heatingelement 113.

FIG. 3A provides a side view of one embodiment of the inner heat chamber114.

In the illustrated embodiment, the heat chamber 114 has an outerdiameter of about 1.125 inches, and a length of about 8.0 inches. Theheat chamber 114 includes outlet port 201 for allowing the heated burstof air to exit from the heat chamber 114. Output nozzle 205 couples tooutlet port 201 and directs the heated burst of air. The heat chamberinlet port 141 is preferably coupled to output end 117 of air conduit116, preferably by welding. The heat chamber 114 causes the air flowingthrough the heater to slow down, compared to the rate at which the airflowed through the air conduit 116. This allows more heat to be absorbedinto the process air.

In a preferred embodiment, the heat chamber 114 encloses the temperaturecontroller 210 (also shown in FIG. 1), which provides measurement andfeedback control of the temperature inside the heat chamber 114.Preferably, the temperature controller 210 is a thermocouple that isinserted into a small-diameter capillary tube 211. The small diametertube 211 is closed at a first end 212, and is open at a second end 213in order to allow for insertion of the thermocouple. The thermocouple210 allows accurate measurement of the process air temperature, withoutadding contamination during the measurement process, since capillarytube 211 prevents exposure of the air in heat chamber 114 to thethermocouple 210.

FIG. 3B illustrates the dimensions of the heat chamber 114, as from atop view. In the illustrated embodiment, the inner diameter of the heatchamber 114 is about 1.0″. The hot air outlet port 201 is shown ashaving a diameter of about 0.25″.

FIG. 4A provides a side view of one embodiment of the spiral-shaped airconduit 116 that surrounds the heater core 112. In this view, the heatercore 112 and heat chamber 114 are not present. The spiral shaped airconduit 116 is preferably made of quartz and forms a helical coildefining a plurality of turns. The outer surface of the heat chamber 114and the inner surface of the helical coil define the gap region 119,which is shaped as a tube-shell so as to allow the heater core 112 to bepress fit into the gap region 119, as is shown in FIG. 2B. As previouslynoted, the spiral-shaped conduit 116 includes an input end 118 and anoutput end 117. The input end 118 is configured to receive air from anair input nozzle of the means 14 for generating bursts of air, whichserves to inject air from the air source 12 (shown in FIG. 1) into theair conduit 116. As described earlier, the output end 117 of conduit 116is welded to the heat chamber inlet port 141 of heat chamber 114,allowing air from the air conduit 116 to enter the heat chamber 114. Theheated air stream exits the chamber 114 from the air outlet port 201.

FIG. 4B illustrates the dimensions of the air conduit 116, as viewedfrom the top. In the illustrated embodiment, the outer spiral conduit116 has an inner diameter of 1.5 inches. The difference between theinner diameter and the outer diameter of the spiral conduit 116 is about0.375 inches, as shown. As described in reference to FIG. 3B, the innerheat chamber 114 has an outer diameter of 1.125 inches. The thickness ofthe shell-shaped gap region 119 formed between the inner chamber and theouter spiral is thus given by:

(1.5−1.125)/2=0.1875 inches.

FIGS. 5A and 5B illustrate heater core 112, constructed in accordancewith a preferred embodiment of the present invention. FIG. 5A provides atop view (not shown to scale) of the heater core 112, whereas FIG. 5Bprovides a side view (both views not shown to scale). In the illustratedpreferred embodiment, the heater core 112 has a cylindrical, tubularconfiguration, and is made of quartz. The heater core 112 preferably hasa wall thickness of about ⅙ inches, and an overall length of about 7inches.

The inner and outer diameters of the heater core 112 are sized so as tofit into the gap region 119 described above. As described with referenceto FIG. 4B, the size of the gap region 119 between the chamber 114 andthe conduit 116 is (1.5−1.125)/2=0.1875 inches=4.7625 mm. The totalspace which needs to be shared by the outer diameter and the innerdiameter of the heater core 112 is therefore given by the differencebetween the size of the gap 119 and the maximum diameter of the quartztube 300:

4.7625 mm−3 mm=1.7625 mm=0.035 inches.

The maximum outer diameter (ODmax) of the heater core 112 is given bythe difference between the inner diameter of the spiral conduit 116 andabout one half of the space shared by the outer and inner diameter ofthe heater core 112, i.e.,:

ODmax (heater core)=1.5 in−0.035 in=1.465 inches.

The minimum inner diameter (IDmin) of the heater core 112 is given bythe sum of the outer diameter of the inner chamber 114 and about onehalf of the space shared by the outer and inner diameters of the heatercore:

IDmin (heater core)=1.125 inner chamber OD+0.035 in=1.16 inches.

The cylindrical heater core 112 has a first end 310 and a second end311. A set of evenly spaced notches 320 are cut out at both ends 310 and311 of the heater core 112. In the illustrated embodiment, each notch320 is about 2 mm wide, and 4 mm deep. The heat generating element 113is a conductive wire wound inner diameter to outer diameter. The notches320 are used to evenly space the wire 113.

FIG. 6 shows a top view of an embodiment of heater core 112, whichincludes heat generating element 113. In a preferred embodiment, theheat generating element 113 may be a conductive filament, such as aheater wire, which generates heat upon application of an electricalpotential across the filament, although other embodiments of theinvention may use other types of heat generating elements. The heatercore 112 preferably operates at a maximum of 500 watts, at 120 Volts.The current through the heat generating element 113 is therefore500/120=4.17 Amps. The heater wire 113 should therefore has a resistanceof about 120/4.17 =28.8 Ohms. In the illustrated embodiment, a 22 gaugeKanthal A1 heater wire, having a length of about 21.5 feet and adiameter of 0.644, is used, although other embodiments of the inventionmay use other types of heater wires, such as Kanthal APM heater wire.The Kanthal A1 22 gauge wire has a resistance of 1.36 Ohms per foot.

The 22 gauge Kanthal A1 heater wire 113 encircling the heater core 112defines conductive coils that surround the cylindrical shell structure.About 21 feet of heater wire 113 is used. The cylindrical heater core ispreferably press fit into the gap 119 between the inner chamber 114 andthe outer spiral conduit 116. Both ends of the heater wire 113 extendout to the back end of the heater 100. An outer case (not shown) may beprovided for the heater 100, preferably made of steel and having anouter diameter of about 4 inches, and a length of about 9 inches. Theheater wire 113 terminates at ceramic terminals that electricallyisolate them from the outer case.

The conductive coils that surround the heater core 112 radiate heatenergy, when a voltage is applied across the coils. The heat energy isradiated both radially inward, toward the heat chamber 114, and radiallyoutward, toward the outer spiral conduit 116 (see FIG. 2B). Inparticular, the conductive coils define a heat flow path for the heatenergy in a first direction radially inward of the coils toward the heatchamber 114, and in a second direction radially outward of the coilstoward the spiral-shaped conduit 116, substantially opposite the firstdirection. Because heat is radiated in both directions, heating takesplace both in the heat chamber 114 and in the conduit 116, increasingthe efficiency of the heating process.

Preferably, the heater core 112 does not have glass to glass contact,either with the inner heat chamber 114 or with the outer spiral conduit116, both of which are preferably made of quartz. It is thus desirablethat there be an inner and outer spacing around the heater core 112, seeFIG. 2B. For this purpose, high temperature buffer material, for exampleceramic tape, may be placed at the top and bottom inner diameter andouter diameter of the heater core 112, to provide insulation. Theceramic tape can be placed over the weld points, at the top and bottomon the inner diameter and the outer diameter of the heater core 112. Thetape may also be wrapped around the outer diameter of the heater core112, and around the ends of the outer spiral conduit 116.

In this embodiment of FIG. 6, the body of the heater core 112 is formedby welding together a plurality of quartz tubes 300, disposed side byside and spaced apart from each other in an annulus so as to form acylindrical shell structure. In the illustrated exemplary embodiment ofthe invention, 34 quartz tubes, each having a length of about 7.5inches, are welded together, 1 inch from both ends, to form acylindrical shell structure. The tubes are spaced apart by about 0.3 mm,on average.

In the illustrated embodiment, the outer diameter of the quartz tubes300 that are used to form the body of the heater core come in incrementsof 1 mm, i.e. the outer diameters of the tubes range may be 1 mm, 2 mm,3 mm, or larger. Since there must be room for the buffer material on theinner diameter and the outer diameter of the heater core, however, thediameter of the quartz tube is preferably not larger than 3 mm. Since 34tubes are used in the illustrated embodiment, each having a diameter of3 mm, and with a 0.3 mm gap between each tube, the circumference of thecylindrical heater core 112, as measured along the center of theconstituent quartz tubes, is about 112.2 mm.

In operation, the solenoid valve (shown in FIG. 1) is activated togenerate a short burst of air, by releasing air pressure from thepressure vessel. The heater is activated by applying an electricpotential through the heater wire 113, so that heat is generated by thewire. The burst of air is injected, using an air injection nozzle, intoan input end of the outer spiral conduit 116 surrounding the heater core112. The burst of air is rapidly heated as the air flows through thespiral conduit 116, and enters the heat chamber 114 which encloses theheat generated by the heater wire 113. The burst of air flows throughthe heat chamber 114, and exits from an outlet port of the heat chamber114. An air output nozzle connected to the outlet port of the heatchamber 114 directs the heated burst of air at the outer coating of anoptical fiber. The air output nozzle is preferably relatively wide, sothat heated air can be directed to the entire stripping length of thefiber. The entire polymer coating on the outside of an optical fiber isvaporized and removed almost instantly.

In various embodiments the stripper or portions thereof are translatablewith respect to the fiber. In other embodiments, the fiber may betranslatable with respect to the stripper, or portions thereof. In suchtranslatable strippers, multiple bursts of air may be used to strip anextended length of fiber, different areas on the same fiber, multiplefibers using the same output nozzle, or some combination thereof.Otherwise, several output nozzles may be provided, each aligned withdifferent fibers or different areas of the same fiber, and the heatchamber 114 outlet port 201 may be translatable (or include atranslatable extension member) such that the outlet port couples to eachof several output nozzles. Otherwise, multiple outlet ports and nozzlemay be provided, and one or more of those may be translatable.

In FIG. 7A, a top view of a translatable stripper 700 is shown. In thisembodiment, the air source 12, filter 34, and means 14 for generatingbursts of air are collectively represented in a single block, forsimplicity. Similarly, the heater 16, temperature controller 210, powersupply 42, and on/off switch 44 are represented by a single block. Inthis embodiment fiber optic cable 50 is supported by two cable supports52, 54. Output nozzle 205 is translatable with respect to the fiber 50(e.g., a titanium dioxide color coded fiber), as indicated the arrowsmarked “A”. To achieve such translation, the output nozzle 205 iscoupled to an electro-mechanical controller 702 that is preferablypreprogrammed for translation and stripping.

For instance, the electro-mechanical controller 702 may bepre-programmed to move the output nozzle along the length of fiber 50for continuous stripping of an extended portion of fiber 50 using aseries of closely spaced bursts (i.e., mulit-burst) of heated air or aprolonged burst (e.g., a burst of about 4-5 seconds) of heated air, orfor spot stripping of predefined portions of fiber 50 with individual orshort bursts (i.e., about 1 second or less) of heated air. Continuous(i.e., either multi-burst or prolonged burst) can also be used onseveral portions of fiber 50.

In FIG. 7B a top view of another embodiment of a translatable stripper710 is shown. In this embodiment, the output nozzle 205 is stationary,but the fiber 50 is translatable, under the control of a fibercontroller 712. The fiber 50 may be translated in one of at least twomanners. First, fiber 50 may be secured in place by cable supports 52,54, and cable supports 52, 54 may move in the direction of arrow A.Second, support 52 may act as a guide and support 54 may include a spoolof fiber optic cable 50. The spool support 54 may be configured to pull(or push) the fiber 50 in the direction of arrow A, which causes it totranslate across an opening of output nozzle 205. Bursts of air areselectively (e.g., with preprogramming and in concert with spool support54) directed from output nozzle 205 to strip fiber 50. Fiber 50 may bestripped along an extended length using the multi-burst or prolongedburst techniques, or fiber 50 may be spot stripped at different placeson the fiber 50 using short burst, multi-burst, or prolonged bursttechniques.

In FIG. 7C is a front view of another embodiment of a translatablestripper 720 is shown. In this embodiment, several fibers 50A, 50B, and50C are loaded into fiber supports 52A & 54A, 52B & 54B and 52C & 54C tobe stripped by a single translatable output nozzle 205. The outputnozzle 205 may be translated in the direction of arrow A or arrow B,under the control of controller 722. Stripper 720 may be programmed forany combination of continuous stripping or spot stripping of any of thefibers 50A, 50B, and 50C. In FIG. 7C, three fibers are shown forillustration, but there is no inherent limit on the number of fibersthat may be stripped. As with the embodiments above, fibers 50A, 50B,and 50C may be stripped along an extended length using the multi-burstor prolonged burst techniques, or fibers 50A, 50B, and 50C may be spotstripped at different places on the fiber 50 using short bursts,multi-burst, or prolonged burst techniques.

FIG. 7D shows a side or top view of the translatable stripper of FIG.7C, but with four fibers 50A, B, C, D being stripped by a single outputnozzle 205. Cable supports are omitted in FIG. 7D.

In FIG. 7E is a front view of another embodiment of a translatablestripper 730 is shown. In this embodiment, the output nozzle remainsstationary and fibers 50A, 50B, and 50C are translatable in thedirection of arrow A and/or arrow B. The fibers are supported or securedby cable supports 52A & 54A, 52B & 54B and 52C & 54C, which move underthe guidance of controller 732. Otherwise, supports 52A, B, C can serveas guides and supports 54A, B, C can be spool supports, as previouslydiscussed. Once again, continuous stripping and spot stripping arepreferably both be accommodated. Fibers 50A, 50B, and 50C may bestripped along an extended length using the multi-burst or prolongedburst techniques, or fibers 50A, 50B, and 50C may be spot stripped atdifferent places on the fiber 50A, 50B, and 50C using short bursts,multi-burst, or prolonged burst techniques.

In FIG. 7F is a front view of another embodiment of a translatablestripper 740 is shown. In this embodiment, the fibers 50A, B, C and theoutput nozzles 205A, B, C are translatable in the direction of arrow Aand/or arrow B. The fibers 50A, B, C move under the guidance ofcontroller 742 (as previously discussed) and the output nozzles 205A,B,Cmove under the guidance of controller 744. Output nozzles 205A, B, C maytake different forms, yielding different output patterns orcharacteristics. Once again, continuous stripping and spot stripping arepreferably both be accommodated. Fibers 50A, 50B, and 50C may bestripped along an extended length using the multi-burst or prolongedburst techniques, or fibers 50A, 50B, and 50C may be spot stripped atdifferent places on the fiber 50A, 50B, and 50C using short bursts,multi-burst, or prolonged burst techniques.

FIG. 7G can be a top or side view of another embodiment of atranslatable stripper 750. In this embodiment, several different outputnozzles 205A, B, C, D may be used, each associated with a differentfiber optic cable 50A, B, C, D. A single outlet port 201′ is provided,configured to selectively couple to each of the output nozzles 205A, B,C, D, shown by dashed ray lines. Outlet port 201′ operates under theguidance of a controller 752, which is preferably preprogrammed toaccomplish desired continuous and spot stripping of fibers 50A, B, C, D.That is, fibers 50A, 50B, 50C and 50D may be stripped along an extendedlength using the multi-burst or prolonged burst techniques, or fibers50A, 50B, 50C and 50D may be spot stripped at different places on thefiber 50A, 50B, 50C and 50D using short bursts, multi-burst, burst, orprolonged burst techniques.

In FIG. 7H, for example, a top or side view of another embodiment of atranslatable stripper 760 is shown. A controller 762 moves the heater 16and output nozzle 205′ in the direction of arrow A, although movement inother directions can also be accommodated. In this embodiment, a wideroutput nozzle 205′ is used, rather than the nozzle 205, to create awider spray for the burst. A prolonged burst may be used as the heater16 and output nozzle 205′ move along the length of the fiber 50. As withother embodiments, the configuration of FIG. 7H may also be adapted tostrip several loaded fibers (e.g., fibers 50A, B, C, and D). Also, aswith other embodiments, the multi-burst or short bursts may be used.Also, the output nozzle 205 of other embodiments could also be used withtranslatable stripper 760, as could output nozzles of otherconfigurations.

In any of the above embodiments of FIGS. 7A-7H, the outlet port 201/201′may an include an extension member configured to couple between theoutlet port and the output nozzle 205/205′. In other embodiments, theentire heater 16 is translatable, such that outlet port 201/201′ andoutlet 205/205′ need not be translatable.

In summary, the method and system of the present invention allows rapidand efficient stripping of optical fibers, without using chemicals. Thevirgin strength of the fiber is not degraded, since no mechanicalscratching of the fiber occurs, and the fiber is not exposed to anyoxidized metal particles, carbon, or other contamination from the heatsource. The method and system of the present invention can be used ontitanium dioxide color coded fiber without degrading the splicestrength. Virtually no coating residue is left on the fiber, and nocurling of the polymer coating is caused, so that no interference iscaused with the next step in optical fiber processing, such as splicing.No rinse step is therefore required, after the fiber has been stripped.Stripping may include translation of the fiber or the heater or portionsthereof. The stripper may be configured to strip several loaded fibers.

While the foregoing has described what are considered to be the bestmode and/or other preferred embodiments, it is understood that variousmodifications may be made therein and that the invention or inventionsmay be implemented in various forms and embodiments, and that they maybe applied in numerous applications, only some of which have beendescribed herein. It is intended by the following claims to claim anyand all modifications and variations that fall within the true scope ofthe inventive concepts.

What is claimed is:
 1. A system for stripping at least one optical fiberhaving an outer coating, the system including: a) an air source; b)means, in operative communication with said air source, for generatingone or more air streams from said air source during a predetermined timeinterval; c) a heater for heating said one or more air streams to apredetermined temperature to remove the outer coating from the at leastone optical fiber, the heater including: i) an isolated air streamtransport path for receiving an air stream from said air source, saidair stream transport path comprising a beat chamber and a first endcoupled to said air source and at least one outlet port; ii) a heatercore having a heat generating element, said heat chamber disposed withinsaid heater core and said heater core configured to allow heat from saidheat generating element to be transferred to said air stream within saidair stream transport path, wherein said air stream is substantiallyheated to said predetermined temperature and remains isolated from saidheater core; iii) at least one output nozzle coupled to said at leastone outlet port and configured to direct said heated air stream ontosaid at least one optical fiber to remove the outer coating from said atleast one optical fiber; and d) a translator in communication with andconfigured to selectively translate at least one of said at least oneoutput nozzle and said at least one optical fiber, to direct said heatedair stream from said at least one output nozzle onto a portion of saidat least one optical fiber to be stripped.
 2. A system according toclaim 1, wherein said predetermined temperature is from about 700degrees C to about 1100 degrees C.
 3. A system according to claim 1,wherein said predetermined time interval is a short burst of said airstream of less than about 1 second.
 4. A system according to claim 1,wherein said portion of said at least one optical fiber to be strippedis an extended portion of said at least one optical fiber and saidpredetermined time interval is a prolonged burst of said air stream ofup to about 5 seconds, wherein said at least one output nozzle istranslated along said extended portion of said at least one opticalfiber during said predetermined time interval.
 5. A system according toclaim 1, wherein said portion of said at least one optical fiber to bestripped is an extended portion of said at least one optical fiber andsaid means for generating one or more air streams generates a pluralityof air stream bursts, wherein said at least one output nozzle istranslated along said extended portion of said at least one opticalfiber.
 6. A system according to claim 1, wherein said at least oneoptical fiber is a plurality of optical fibers and said translator isconfigured to selectively position said at least one output nozzle ateach of said plurality of optical fibers.
 7. A system according to claim1, wherein said translator is configured to position said at least oneoutput nozzle at a plurality of portions on a single optical fiber to bestripped.
 8. A system according to claim 1, wherein said translator isconfigured to position said at least one output nozzle at a plurality ofportions on said at least one optical fiber.
 9. A system according toclaim 1, wherein said translator is configured to translate a pluralityof optical fibers and a plurality of output nozzles.
 10. A systemaccording to claim 1 wherein said at least one optical fiber is aplurality of optical fibers.
 11. A system for stripping at least oneoptical fiber having an outer coating, the system including: a) an airsource; b) means, in operative communication with said air source, forgenerating one or more air streams from said air source during apredetermined time interval; c) a heater for heating said one or moreair streams to a predetermined temperature to remove the outer coatingfrom the at least one optical fiber, the heater including: i) anisolated air stream transport path for receiving an air stream from saidair source, said air stream transport path comprising a heat chamber anda first end coupled to said air source and at least one outlet port; ii)a heater core having a heat generating element, said heat chamberdisposed within said heater core and said heater core configured toallow heat from said heat generating element to be transferred to saidair stream within said air stream transport path, wherein said airstream is substantially heated to said predetermined temperature andremains isolated from said heater core; iii) at least one output nozzlecoupled to said at least one outlet port and configured to direct saidheated air stream onto said at least one optical fiber to remove theouter coating from said at least one optical fiber; and d) a translatorin communication with said heater and configured to translate saidheater.
 12. A method for stripping at least one optical fiber having anouter coating, the method comprising: A. generating air stream burstsfrom an air source; B. providing a heater comprising: i) an isolated airstream transport path comprising a heat chamber and having a first endcoupled to said air source and at least one outlet port; and ii) aheater core having a heat generating element, said heat chamber beingdisposed within said heater core; C. heating said heat chamber bygenerating heat from said heat generating element of said heater core;D. transporting one or more of said air stream bursts from said airsource to said heat chamber; E. heating one or more of said air streambursts within said heat chamber to a predetermined temperature to removesaid outer coating from said at least one optical fiber, while isolatingsaid one or more air stream bursts from said heater core; F. providingat least one output nozzle for coupling to said heat chamber; G.directing one or more of said air stream bursts from said heat chamberto said at least one output nozzle; H. translating one or more of saidat least one output nozzle and said at least one optical fiber, andaligning said at least one output nozzle with a portion of said at leastone optical fiber to be stripped; and I. directing one or more of saidair stream bursts from said output nozzle onto said at least one opticalfiber, so as to thermally remove the outer coating from said at leastone optical fiber.
 13. A method according to claim 12, wherein saidpredetermined temperature is between about 700 degrees to about 1100degrees.
 14. A method according to claim 12, wherein one or more of saidair stream bursts have a short duration of less than about 1 second. 15.A method according to claim 12, wherein said portion of said at leastone optical fiber to be stripped is an extended portion and one or moreof said air stream bursts have a prolonged duration of up to about 5seconds.
 16. A method according to claim 12, wherein said portion ofsaid at least one optical fiber to be stripped is an extended portion ofsaid optical fiber and one or more of said air stream bursts iscomprised of a series of bursts each having a duration of less thanabout 1 second..
 17. A method according to claim 12, wherein step Hincludes translating a plurality of output nozzles or a plurality ofoptical fibers.
 18. A method for stripping at least one optical fiberhaving an outer coating, the method comprising: A. generating air streambursts from an air source; B. providing a heater comprising: i) anisolated air stream transport path comprising a heat chamber and havinga first end coupled to said air source and at least one outlet port; andii) a heater core having a heat generating element, said heat chamberbeing disposed within said heater core; C. heating said heat chamber bygenerating heat from said heat generating element of said heater core;D. transporting one or more of said air stream bursts from said airsource to said heat chamber; E. heating one or more of said air streambursts within said heat chamber to a predetermined temperature to removesaid outer coating from said at least one optical fiber, while isolatingsaid one or more air stream bursts from said heater core; F. providingat least one output nozzle for coupling to said heat chamber; G.directing one or more of said air stream bursts from said heat chamberto said at least one output nozzle; and H. translating said heater todirect one or more of said air stream bursts from said output nozzleonto said at least one optical fiber, so as to thermally remove theouter coating from said at least one optical fiber.